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I've got a lead on an NZDM SF Forester gearbox for the 1.447:1 DR gearset. If I get this gearbox, I'd be combining it with a DCCD STi gearbox - swapping in the helical LSD, DCCD centre and 4.44 gearing. I'd get a 4.44 vLSD to match out back.

Just wondering if the 1.447 dual range will fit with the 4.44 gears without colliding?

I've got a lead on an NZDM SF Forester gearbox for the 1.447:1 DR gearset. If I get this gearbox, I'd be combining it with a DCCD STi gearbox - swapping in the helical LSD, DCCD centre and 4.44 gearing. I'd get a 4.44 vLSD to match out back.

Just wondering if the 1.447 dual range will fit with the 4.44 gears without colliding?

Cheers

My understanding is no. There is more to take off the crown wheel than the 1.59. Also the individual gearing on the STI box is all wrong for offroad applications. Designed to keep the boxer on boost between gears.

Is this a practical/realistic plan? I realise some parts may need machining to fit, and that it will rev a bit high at 100 with the factory SG 5th and the 4.44 diffs, but currently I can cruise at 100 pulling 2500rpm with 215/65 tyres, 4.11 diffs and the SG gearbox so I'm not too worried if it revs a bit higher, though over 3000 would be excessive. I'm not going to build off my current box as the synchros are on their way out on all gears except 5th.

Long-term, I aim to get a 4.44 R180 and swap in an ARB airlocker, to create an AWD Subie with twin lockers and a front LSD! I see no reason why this shouldn't work.

Reviving this thread for the sake of starting a new one. Had a few hours to kill today and started thinking about Subaru diff locks again (yes, I know...).

The 4.44 r180 used in GC STis has an 8-bolt crown gear. Most r180s used in Nissan 4x4 applications use a 10-bolt crown gear. However, D21/D22 Nissans use an 8-bolt crown gear (according to ARB's application guide).

Therefore, the ARB RD182 air locking differential carrier should be a direct swap into a 4.44 8-bolt crown gear STi r180 differential.

The 4.44 r180 used in GC STis has an 8-bolt crown gear. Most r180s used in Nissan 4x4 applications use a 10-bolt crown gear. However, D21/D22 Nissans use an 8-bolt crown gear (according to ARB's application guide).

Therefore, the ARB RD182 air locking differential carrier should be a direct swap into a 4.44 8-bolt crown gear STi r180 differential.

I'm not sure this would work as just because they have the same number of bolts doesn't meant they have the same PCD. There may be other differences too

I'm not sure this would work as just because they have the same number of bolts doesn't meant they have the same PCD. There may be other differences too

Double-checked the PCDs. All 8-bolt R180 differentials with the 115 mm crown wheel use the same 135 mm PCD.

However, early 4.44 Subaru R180s use a 25-spline output shaft, whereas the later 3.X ratio R180s use a 27-spline output shaft (same as Nissan R180s and the ARB locker). Therefore, it is in theory possible to install an ARB RD182 8-bolt air locker into an early 4.44 Subaru R180, but you will have to use GD-on 27 spline inner CVs.

Still, the R160 locker would make life a lot easier and cheaper by being compatible with every other Subaru.

A rear locker would be cool but on the 5MT it won't help much because the center Vlsd is a bit weak at 4 kg so all the traction would go to the front, on the wheel with the less traction. Options are DCCD or 12 kg center Vlsd.

With a 4EAT, a switch to lock the MPT and you're done ! Or swap for a 4EAT with VTD.

A rear locker would be cool but on the 5MT it won't help much because the center Vlsd is a bit weak at 4 kg so all the traction would go to the front, on the wheel with the less traction. Options are DCCD or 12 kg center Vlsd.

With a 4EAT, a switch to lock the MPT and you're done ! Or swap for a 4EAT with VTD.

Yup, if I ever went to the trouble of installing a rear on locker on any future Subaru I own it'll be in combo with an upgraded gearbox, either auto centre lock mod or DCCD for a manual (relatively easy to find in JDM-rich NZ).

A rear locker would be cool but on the 5MT it won't help much because the center Vlsd is a bit weak at 4 kg so all the traction would go to the front

Not quite true, I have a clutch rear LSD with a bog stock centre diff, 4kg viscous LSD. There have been many times the rear LSD has kept driving me forward with diagonally lifted wheels, even up a steep hill.

If the centre diff is in good working condition, it does a good job of transferring power to the rear. You can see the front wheel is completely off the ground but the rear wheel keeps turning: